/* tinyproxy - A fast light-weight HTTP proxy
 * Copyright (C) 1998 Steven Young <sdyoung@miranda.org>
 * Copyright (C) 1999-2003 Robert James Kaes <rjkaes@users.sourceforge.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

/* Misc. routines which are used by the various functions to handle strings
 * and memory allocation and pretty much anything else we can think of. Also,
 * the load cutoff routine is in here. Could not think of a better place for
 * it, so it's in here.
 */

#include "main.h"

#include "conns.h"
#include "heap.h"
#include "http-message.h"
#include "log.h"
#include "utils.h"

/*
 * Build the data for a complete HTTP & HTML message for the client.
 */
int send_http_message(struct conn_s *connptr, int http_code, const char *error_title, const char *message) {
static const char *headers[] =
{
	"Server: " PACKAGE "/" VERSION,
	"Content-type: text/html",
	"Connection: close"
}
;

http_message_t msg;

msg = http_message_create(http_code, error_title);
if (msg == NULL)
return -1;

http_message_add_headers (msg, headers, 3);
http_message_set_body( msg, message, strlen( message));
http_message_send (msg, connptr->client_fd);
http_message_destroy( msg);

return 0;
}

/*
 * Safely creates filename and returns the low-level file descriptor.
 */
int create_file_safely(const char *filename, unsigned int truncate_file) {
struct stat lstatinfo;
int fildes;

/*
 * lstat() the file. If it doesn't exist, create it with O_EXCL.
 * If it does exist, open it for writing and perform the fstat()
 * check.
 */
if (lstat(filename, &lstatinfo) < 0) {
	/*
	 * If lstat() failed for any reason other than "file not
	 * existing", exit.
	 */
	if (errno != ENOENT) {
		fprintf(stderr, "%s: Error checking file %s: %s\n", PACKAGE, filename, strerror(errno));
		return -EACCES;
	}

	/*
	 * The file doesn't exist, so create it with O_EXCL to make
	 * sure an attacker can't slip in a file between the lstat()
	 * and open()
	 */
	if ((fildes = open(filename, O_RDWR | O_CREAT | O_EXCL, 0600)) < 0) {
		fprintf(stderr, "%s: Could not create file %s: %s\n", PACKAGE, filename, strerror(errno));
		return fildes;
	}
} else {
	struct stat fstatinfo;
	int flags;

	flags = O_RDWR;
	if (!truncate_file)
		flags |= O_APPEND;

	/*
	 * Open an existing file.
	 */
	if ((fildes = open(filename, flags)) < 0) {
		fprintf(stderr, "%s: Could not open file %s: %s\n", PACKAGE, filename, strerror(errno));
		return fildes;
	}

	/*
	 * fstat() the opened file and check that the file mode bits,
	 * inode, and device match.
	 */
	if (fstat(fildes, &fstatinfo) < 0 || lstatinfo.st_mode != fstatinfo.st_mode || lstatinfo.st_ino != fstatinfo.st_ino
			|| lstatinfo.st_dev != fstatinfo.st_dev) {
		fprintf(stderr, "%s: The file %s has been changed before it could be opened\n", PACKAGE, filename);
		close(fildes);
		return -EIO;
	}

	/*
	 * If the above check was passed, we know that the lstat()
	 * and fstat() were done on the same file. Now we check that
	 * there's only one link, and that it's a normal file (this
	 * isn't strictly necessary because the fstat() vs lstat()
	 * st_mode check would also find this)
	 */
	if (fstatinfo.st_nlink > 1 || !S_ISREG(lstatinfo.st_mode)) {
		fprintf(stderr, "%s: The file %s has too many links, "
				"or is not a regular file: %s\n", PACKAGE, filename, strerror(errno));
		close(fildes);
		return -EMLINK;
	}

	/*
	 * Just return the file descriptor if we _don't_ want the file
	 * truncated.
	 */
	if (!truncate_file)
		return fildes;

	/*
	 * On systems which don't support ftruncate() the best we can
	 * do is to close the file and reopen it in create mode, which
	 * unfortunately leads to a race condition, however "systems
	 * which don't support ftruncate()" is pretty much SCO only,
	 * and if you're using that you deserve what you get.
	 * ("Little sympathy has been extended")
	 */
#ifdef HAVE_FTRUNCATE
	if (ftruncate (fildes, 0) != 0)
	{
		log_message (LOG_WARNING,
				"Unable to truncate file '%s'", filename);
	}
#else
	close(fildes);
	if ((fildes = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0600)) < 0) {
		fprintf(stderr, "%s: Could not open file %s: %s.", PACKAGE, filename, strerror(errno));
		return fildes;
	}
#endif /* HAVE_FTRUNCATE */
}

return fildes;
}

/**
 * pidfile_create:
 * @filename: The name of the file which should be created.
 *
 * Creates a file with the PID of the Tinyproxy process.
 *
 * Returns: %0 on success, non-zero values on errors.
 **/
int pidfile_create(const char *filename) {
int fildes;
FILE *fd;

/*
 * Create a new file
 */
if ((fildes = create_file_safely(filename, TRUE)) < 0)
	return fildes;

/*
 * Open a stdio file over the low-level one.
 */
if ((fd = fdopen(fildes, "w")) == NULL) {
	fprintf(stderr, "%s: Could not write PID file %s: %s.", PACKAGE, filename, strerror(errno));
	close(fildes);
	unlink(filename);
	return -EIO;
}

fprintf(fd, "%d\n", getpid());
fclose(fd);
return 0;
}
